Cancer Of The Lung

High occurrence of lung cancer and poor survival rates make it a very important public health problem, and also a leading cause of cancer death in the world. Most patients have locally advanced lung cancer at the time of diagnosis.

As per the Madras Metropolitan Tumour Registry (MMTR) Chennai, in 2006-2008, cancer of the lung was the most common among males, and was ranked among the top ten in females. It constituted 10.9 per cent and 3.3 per cent of all cancers among males and females respectively.

Risk factors

Cigarette smoking is the single highest cause for lung cancer epidemic

Other contributing factors are asbestos, arsenic, chromium, nickel, and radon in the work environment

Other environmental factors such as passive smoking and air pollution

Molecular changes that commonly occur in lung cancer are mutations of tumour suppressor genes p16, p53, and H, K, N-ras family of oncogenes

Studies have shown that individuals with a higher dietary intake of fruits or vegetables have lower risk of lung cancer

Types

Lung cancers are classified into:

Non-Small Cell Carcinoma (NSCLC) that include squamous cell carcinoma, adenocarcinoma, large cell carcinoma and their subtypes (80 per cent)

Small Cell Carcinoma (SCLC) (20 per cent)

There are other rare types of lung cancers that can occur apart from these

Poor prognostic factors include higher tumour size and extent, regional nodal involvement, absence or presence of distant metastasis, weight loss of more than 10 per cent, age less than 40 years, tumour size more than 3 cm, lymphovascular invasion, and mutation of the tumour suppressor gene p53.

Spread

Spread can occur along bronchus into lung parenchyma, to mediastinum or pleura causing pleural effusion. Diaphragm and chest wall involvement are not uncommon. 50 per cent have nodal metastasis at resection. Distant spread commonly involves adrenals to 50 per cent, liver to 30 per cent, apart from brain, bone opposite lung, pericardium and kidneys.

At present, screening for early detection of lung cancer is not recommended, probably because of the failure of early studies to demonstrate any mortality reduction from lung cancer evaluation based on sputum cytology and/or chest radiography. With the introduction of helical computerised tomography, a new imaging modality that can detect nodules as small as a few millimetres, the potential benefits of lung cancer screening is being re-examined.

Imaging in lung cancer

Chest radiography remains the basic modality for the detection of lung cancer.

Positron emission tomography (PET) is a molecular imaging modality that detects metabolic changes in tumour cells. PET improves the rate of detection of the extent of primary tumour, draining nodes and distant metastases, thereby improving the staging accuracy in patients with NSCLC that can have a significant impact on clinical management.

Other diagnostic modalities

Clinical and radiological findings should guide the diagnostic approach, depending on the size and location of the tumour, the presence of metastatic disease, and the clinical status of the patient. Diagnostic and staging work is taken up concomitantly.

Surgery is the preferred modality of primary management for resectable NSCLC.

Based on initial stage and postoperative histopathological report, patients will be planned for adjuvant radiation therapy with or without chemotherapy, or chemotherapy with or without radiation therapy.

For medically inoperable and unresectable tumours chemoradiation therapy is the preferred line of management.

With the rapid technological explosion in diagnostic imaging and radiation delivery techniques, radiation oncologists are now able to deliver external beam radiation therapy with high precision using Image Guided Intensity Modulated Radiation Therapy (IG IMRT), Stereotactic Body Radiosurgery real time positional management respiratory gating system delivering significantly higher doses to the tumour and minimum dose to the surrounding normal lung and other critical structures like the opposite lung, heart, spinal cord, oesophagus, and breast, resulting in increased cure rates and lesser side effects respectively.

Radiation along with chemotherapy has a role in palliation of symptoms due to recurrent, advancing and metastatic cancer.